The present invention relates to a double-split cage used for a roller bearing.
Conventionally, two semi-cylindrical cages are used by combining it with each other. The double-split cage is formed into a semi-cylindrical shape and provided with pockets for accommodating rollers at several positions in the circumferential direction (refer to Japanese Utility Model Publication Hei. 06-6746).
This double-split cage is manufactured so that the pockets for accommodating rollers are formed through a long strip-shaped metallic sheet and the long strip-shaped metallic sheet is curved into a semicircular shape and cut off. In this case, a portion of the pillar portion located between the pockets in the circumferential direction is cut.
When the strip-shaped metallic sheet is cut off at the position of the pillar portion, the width of the pillar portions in the circumferential direction located at opposite end portions of the strip-shaped metallic sheet in the circumferential direction is reduced after the completion of cutting. Therefore, the mechanical strength of the pillar portion deteriorates and the durability is deteriorated. In order to solve the above problems of lack of the mechanical strength, it could be considered that the width in the circumferential direction of the pillar portions to be cut is made to be larger than the width in the circumferential direction of the other pillar portions. However, in this case, the machining becomes complicated because the punching pitch must be changed when the pockets are formed by means of punching.
On the other hand, when the strip-shaped metallic sheet is cut off, it is possible to cut off the strip-shaped metallic sheet at the position of the pocket. In this case, as shown in FIG. 10, protrusions 81a, 81b, 82a, 82b are formed on opposite end sides in the axial direction at opposite end portions in the circumferential direction of the double-split cage 80. In the case of this double-split cage 80, the following problems may be encountered. When two cages, which are formed into a pair, are incorporated into a place where the double-split cages 80 are used, if the pair of double-split cages 80, 80 are shifted in the axial direction, the protrusions 81a, 81b, 82a, 82b at opposite end portions in the circumferential direction of the two double-split cages 80, 80 may be hooked at each other. In order to solve this problem, the positional correction should be conducted to shift the two double-split cages 80, 80 in the axial direction so that they can be appropriately opposed to each other. However, since the protrusions 81a, 81b, 82a, 82b of the two double-split cages 80, 80 are overlapped and hooked at each other in the axial direction, it becomes difficult to correct the shift of the protrusions.
In this connection, as shown in FIG. 12, in the case of the double-split cage 80 having the pockets 84 in which two rows of rollers 83 are accommodated in the axial direction, if cutting is conducted so that the strip-shaped sheet is cut off in the width in the circumferential direction of the pocket 84 in the manufacturing process, the protrusions 81a, 81b, 81c, 82a, 82b, 82c are formed at three positions in the axial direction in the same manner as described above. Accordingly, the same problems as those described above are caused as shown in FIG. 13.